the breaking news out of utah. A speedy verdict in the trial of a doctor accused of murdering his beauty queen wife in the bathtub of their suburban family home. All to make room, allegedly, for his young mistress. The jury came back in the middle of the night with a verdict. Guilty. In a moment, we'll hear from our chief legal analyst, dan abrams. First, here's abc's aditi roy. Aditi, good morning. Reporter: Good morning, dan. It was a late night for jurors. The verdict was read in the middle of the night. THE JURY FOUND martin MacNeill guilty of murder and obstruction of justice, after deliberating for 11 hours. We, the jury, having reviewed the evidence in the case, find the defendant, to count one, murder in the first-degree. Reporter: Morton mackneel's daughters sobbing, while they're father remained expressionless. Family members smoke about the crusade. We're so happy he can't hurt anyone else. We can finally take a deep breath and put it behind us. Reporter: The jury found MacNEILL GUILTY OF MURDER AND Obstruction of justice, after 11 hours of deliberation. Jurors sat through 13 days of testimony, with more than 5 dozen witnesses during the month-long trial. martin MacNeill murdered his wife, michele. Reporter: Macneill was convicted of killing his wife, michele, by giving her a fatal dose of painkillers and placing her in a tub, while she was recovering from plastic surgery. The prosecution says his motive was to continue an affair. MacNEILL SAID HE WAS INNOCENT. His lawyers argued michele MacNEILL DIED OF A HEART Disorder. Both sides spoke after the verdict. I'm disappointed. But I don't have comments. Reporter: The prosecution put MacNEILL'S DAUGHTERS ON THE Stand, as well as two former INMATES with MacNeill, saying he confessed to the murder. The defense maintained there was not enough evidence to convict MacNEILL. martin MacNeill faces life in prison. He is scheduled to be sentenced ON JANUARY 7th. For more on this, let's bring in our chief legal analyst, and co-anchor of "nightline," dan abrams, who was covering this trial from the start. 11 hours. A lot of people think it should have been an open and shut case. 11 hours, not that quick for this kind of case. So, a little easier to get unanimity among them, rather than a 12-person jury. The key question in this case, are the jurors going to be convinced beyond a reasonable doubt that she died at his hands. That was it. The medical examiner said we can't determine whether this was a murder for sure. Initially they said it was natural causes. That was always the problem for prosecutors in this case. Can they prove that this is a murder at all? Seems the jurors believed it was. Even if they could prove he wasn't a great guy. Even the defense can see he's not a great guy. He's an awful guy. The defense was coming forward and admitting that. Saying that doesn't mean he's a murderer. It would have been coincidental, if this guy having an affair, seemingly ovdicating his wife, et cetera, luckily would have dropped dead at the same time. We we have gotten to this point to without the activeness of his daughters? Absolutely not. His daughters kept coming forward. They started to learn a lot more ABOUT martin MacNeill falsifying documents. Getting arrested later on for stealing an identity of one of his daughters. Crazy stuff they learned once the daughters got the authorities to look into this. And finally, quickly, does he have any shot at appeal here? Long shot. Yes, he'll appeal. Not a good shot. He's probably going to get a very stiff sentence here. This is his best hope, was here during the trial. Quite a story. And dan abrams, always great to have your analysis. We're going to turn to the other top story developing overnight.

This transcript has been automatically generated and may not be 100% accurate.

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